1. Field of the Invention
The present invention relates to a three-dimensional image display, and more particularly, to a three-dimensional image display capable of reducing a difference between a resolution variation rate in a pixel column direction and a resolution variation rate in a pixel row direction and preventing a color separation phenomenon.
2. Discussion of the Related Art
One factor for recognizing a three-dimensional image is a binocular disparity phenomenon in which images viewed in different directions are perceived by a viewer's eyes. Different two-dimensional images perceived by the viewer's eyes are synthesized by the user's brain so as to be viewed as a three-dimensional image. A three-dimensional image display allows a viewer to view a three-dimensional image using the binocular disparity phenomenon. That is, the three-dimensional image display allows the viewer to view the three-dimensional image by allowing different disparity images to be perceived by the viewer's left eye and right eye.
In order to realize the three-dimensional image display, various methods of allowing different images to be perceived by a viewer's eyes have been studied. Among them, as shown in FIGS. 1 and 2, there is a lenticular lens type three-dimensional image display.
Referring to FIG. 1, a lenticular lens type three-dimensional image display is formed by attaching a lenticular sheet 21 including a lenticular lens array to a display panel 11. The path of a two-dimensional image displayed on the display panel 11 is divided by lenses of the lenticular sheet 21. In more detail, an image incident to the left side of a convex lens is refracted toward the viewer's right eye through the lens and an image incident to the right side of the convex lens is refracted toward the viewer's left eye by the lens. The two-dimensional images perceived by the left eye and the right eye are recognized by the viewer as the three-dimensional image.
A simple method of realizing the three-dimensional image using the lenticular sheet 21 is a 2-view method of alternately arranging two images including a left-eye image and a right-eye image in a pixel column direction x of the display panel 11, as shown in FIG. 2. In the 2-view method, the left-eye image is perceived by the viewer's left eye through the lens and the right-eye image is perceived by the viewer's right eye such that the viewer recognizes the three-dimensional image. The number of disparity images which are actually viewed by the viewer is infinite. However, in the 2-view method, since only the two disparity images are viewed so as to realize three-dimensional effect, the three-dimensional effect is unnatural.
Recently, in order to realize more natural three-dimensional effect, multi-view methods which are obtained by increasing the number of disparity images, such as a 4-view method, a 9-view method, a 36-view method, a 60-view method and a 72-view method, have been developed.
As the number of views is increased, a difference between a resolution variation rate in a pixel column direction x and a resolution variation rate in a pixel row direction y of the three-dimensional image display is increased. In order to solve this problem, the lenticular sheet 21 is provided in front of the display panel 11 such that the long axes L of the lenses included in the lenticular sheet 21 is inclined with respect to the pixel row direction y.
Hereinafter, in the 9-view method, for example, the resolution variation rate in the pixel column direction x and the resolution variation rate in the pixel row direction y of the three-dimensional image display according to the increase in number of views will be described with reference to FIGS. 3A and 3B. In the 9-view method, a group g includes first to ninth disparity images which are displayed in subpixels in one-to-one correspondence. The disparity images having the same number are images photographed in the same direction and the disparity images having adjacent numbers are images photographed in adjacent directions.
As shown in FIG. 3A, the same disparity images are displayed in the pixel row direction y of the display panel 11 and the first to ninth disparity images are sequentially displayed in the pixel column direction x. If the long axes L of the lenses of the lenticular sheet 21 are aligned in parallel in the pixel row direction y of the display panel 11, the resolution in the pixel row direction y does not deteriorate, but the resolution in the pixel column direction x is reduced to 1/9. The deterioration of the resolution in the pixel column direction x is increased as the number of disparity images is increased. Since the deterioration of the resolution is increased in only the pixel column direction x, the image quality of the three-dimensional image perceived by the viewer deteriorates.
In order to prevent the deterioration of the resolution in only the pixel column direction x, as shown in FIG. 3B, the first to ninth disparity images are distributed and displayed in the pixel column direction x and the pixel row direction y of the display panel 11 such that the long axes L of the lenses are obliquely aligned relative to the pixel row direction y. At this time, the same disparity images included in the respective groups g are distributed in subpixels 31 of different colors R, G and B, in order to realize a multi-color image.
An angle between the long axes L of the lenses and the pixel row direction y is a value for allowing the subpixels 31 of different colors, in which the same disparity images are displayed, to be adjacent to each other. The value of the angle suggested is about 9.46° (=arctan(⅙)).
If the angle between the long axes L of the lenses and the pixel row direction y is 9.46° (=arctan(⅙)), the resolution in the pixel column direction x is reduced to 1/n/2 (n is the number of views, that is, the number of disparity images). That is, as shown in FIG. 3B, in the 9-view method, the resolution in the pixel row direction y is reduced to ½ and the resolution in the pixel column direction is reduced to 1/4.5. By obliquely aligning the long axes L of the lenses, a difference between the resolution variation rate in the pixel row direction y and the resolution variation rate in the pixel column direction x is reduced compared with that shown in FIG. 3A and an image quality deterioration phenomenon can be suppressed.
Although the long axes L of the lenses are obliquely aligned by 9.46° (=arctan(⅙)) relative to the pixel row direction y so as to suppress the image quality deterioration phenomenon, the long axes L of the lenses may be obliquely aligned by other angles. As described above, even when the long axes L of the lenses are obliquely aligned by any angle relative to the pixel row direction y, the same disparity images may be displayed in subpixels of different colors in order to realize a multi-color image. The adjacent subpixels of different colors R, G and B, in which the same disparity images are displayed, are arranged as shown in FIGS. 4A and 4B.
The multi-color image is realized by overlapping red (R), green (G) and blue (B) colors. However, since the same disparity images are included in different groups g, the subpixels of red (R), green (G) and blue (B) color for realizing the multi-color image are too separated from one another and thus an overlap area may not be generated. Accordingly, the viewer cannot recognize the multi-color image which is displayed by overlapping red (R), green (G) and blue (B) colors and can recognize the respective separated colors.
As described above, in the related art three-dimensional image display, the long axes of the lenticular lenses are inclined by a predetermined angle relative to the pixel row direction such that the difference between the resolution variation rate in the pixel column direction and the resolution variation rate in the pixel row direction is reduced and the image quality of the three-dimensional image is improved. However, the angle between the pixel row direction and the long axes of the lenticular lenses causes another image quality deterioration problem, that is, a color separation phenomenon.